1. Field of the Invention
The present invention relates to the field of radar systems and methods.
2. Prior Art
Conventional radar scans the environment with a narrow beam, dwelling in each beam position for a relatively short time, typically for a few milliseconds. Such a short time is adequate for the detection of targets in thermal noise. However, since targets usually must be tracked, the beam must revisit each target position sufficiently often to maintain track on all targets. This flexibility in the scheduling of beam positions is achieved with a phased array antenna. The phasing of the array elements is controlled so that the beam can be pointed in any arbitrary direction, within limits, at any time.
This flexibility in orienting the beam solves only part of the radar problem. Tasks such as target detection in clutter and target analysis (discrimination, classification or identification) require relatively long dwell times on each target, perhaps as much as one second in the case of target analysis. In most applications the radar must also accommodate multiple targets within the search space, and the number can be quite large. The problem then is to provide the required dwell time on each target as well as rapid updates on those in track, and yet still continue to search for new targets, all within a reasonable search frame time.
This common radar problem cannot be solved by beam pointing agility. It can be solved by broadening the transmit beam and implementing multiple simultaneous receive beams, which also requires multiple receivers (the number is approximately the same as the number of simultaneous beams). In order to provide both sufficiently long dwell times and rapid track updates, the number of receivers can be quite large, leading to a very complex and expensive radar system.